
You Must have an Xbox 360 memory unit and transfer cable, or an Xbox 360 Hard drive transfer cable.
Everything you need to mod your gamertag can be downloaded Here
Start by opening up your profile in Modio along with Mitchboy999's Microsoft profile

Extract the account file's out of each profiles to seperate folders

Decrypt both account files using siggggggggggy

Open both account files in HxD and Select the area shown below and copy from your profile

into the 'Microsoft' profile

If you wish, you can change the gamertag to whatever you like, but make sure not to overwrite the dot with the value of 09 at the end of the gamertag. Although the 'Microsoft' profile is larger than 15 characters creating a new gamertag of this length will not work.
Here are the colour and button codes for your gamertag. Note: colours may vary as they have been taken from CoD waw
^0 = black
^1 = red/orange
^2 = lime green
^3 = yellow
^4 = navy blue
^5 = light blue
^6 = gold
^7 = pink
^8 = white turns gray after a game is played
01 = A
02 = B
03 = X
04 = Y
05 = L1
06 = R1
0E = Start
0F = Select
10 = L3
11 = R3
12 = L2
13 = R2
14 = D pad Up
15 = D pad Down
16 = D Pad Left
17 = D Pad Right
Here is an example of how to use these codes

Now you can save the account File and encrypt it with siggggggggggy
Then overwrite the account in the 'Microsoft' profile with the one you just modded

Now rehash and resign the profile

After you have rehahsed and resigned the modded profile create a new folder called E0000314FA661947, inside that folder create a new folder called FFFE07D1, and finally another folder inside that called 00010000.Then the modded profile should be placed into the 00010000 folder.

Then drag the whole E0000314FA661947 folder into Partition 3/Content for Hard drive and Partition 1/Content for Memory Unit using either explorer 360 provided in the download or xport360.

After Modding your account, follow this video to change your gamertag
https://www.youtube.com/watch?v=2mf6PZniJ3M&feature=player_embedded